Photoelectric relay



Feb; 25, 1947. H REYNOLDS 2,416,595

PHOTO ELECTRIC RELAY Filed March 15, 1944 12 10a 22 @4501mumnmmgmiaga 3nventor azzzes 17. Reynolds 0am Gttorneg Patented-Feb. 25, 1947 James H. Reynolds, Indiananoliajlndg, assignor 1 to Radio Corporation of, America, a corporationof Delaware ApplicationMarch 15, 1944, Serial No. 526,524

This invention relates to a photo-electric relay, and particularlyto such a relay adapted to con trol the movement of objects in spaced relation.

In many automatic industrial processes, it frequently becomes necessary'tomove objects from one station to another with an interval of time and space between each object. The moving process is usually an automatic one. If the objects become jammed on the conveyor'or other track along which they are being moved, the

moving means will, nevertheless, continue to operate and damage may be caused to the objects and their contents and, perhaps more importantly, to the equipment. Delay may also be caused in shutting down the machinery for the repairs which may then be' necessary.

It is, therefore, an object of the invention to provide an improved photo-electric relay adapted to control the movement of objects in spaced rela- 1 tion.

Another object is to provide means for auto.- matically rendering inoperative means for moving objects along a path in spaced relation, when such objects become jammed together on said A path.

An additional objectis to provldean improved photoelectric circuit which will be energized when light passing to an element therein is interrupted for more than a predetermined period.

A further object is to provide an improved photoelectric relay adapted'to be operated by a lternating currents only, and including :a time delay circuit.

' A still further object is to provide an improved and compact photo-electric relay for the purposes aforesaid from whichconnections need be made only to a source of'alternat-ing currents and to the means for moving such objects.

These objects are achieved in accordance with '8 Claims. (01.250.24.15

' circuit,.although the passage. ,of light to the photo- 'ternating current. A beam of light :is directed to the photo-electric device in such-manner that each object cuts thebeam in its passage along the conveyor, Light passing to the cathode of the photo-electric device causes currentto flow therefrom to the grid of the gas tube, fires :the

electric device is intermittently interruptedrby the normal passage of the objects along the COD: veyor. If, however, the passage of light to the photo..-.e1.e.ctric device should be interrupted for a 7 period greater than the delay caused by the time delay circuit (for example, because the objects have :become jammed against each other on theconveyor), the gas tube is extinguished; this opens the relay which in turn stops further movement of the objects along the conveyor.

From time to time in this specification refer,- ence will be made toautomatic apparatus for the processing of bottles containing beverages.

In such apparatus, filled bottles are moved auto.- matically in an upright position, and in spaced relation to each other along a conveyor from,a

machine at which they. are inspected for the detection of foreign particles which may be con.-

tained in the beverage, to another machine at which the bottles .are capped. The references .to such apparatus are inserted for purpose of illustrationonly, since the invention is applicable to any apparatus in which any light-impeding objects are moved in spaced relation, and no limitation of the scope, of the invention is intended by such references.

The invention maybe better understood from a consideration of the following description thereof when read/in conjunction with the ac-' companying dra-wingswi-n which:

photo-electric control of the invention to. objects moving along a conveyor,

Figure '2 is a circuit diagram of apparatus in one embodiment of the invention, and

Figure); is a iview in elevation .along the conveyoril'lustrati-ng adjustment of the path of the flight from its source :to the photo-tube.

Figure 1 shows apparatus 14 which may ,be the inspection machine before referred to, and a conveyorzll. Objects Illa, 1%, etc. .(for example, bottles) are moved by any appropriate means, such as the electric motor .3, from the machine l natheconvevor12in the' i ect on of th arrow. Adjacent tothe conveyor 12 is the photoelectric control 16 of the invention. The control includes a source .of light suc as t e citer lamp :l'8.;..;in ;a preferred embodimenta 21 candlep w r. sin le c ntact, to .8 olt a 7 bulbha b en useda t e s i ce of l ght- L t from the lamp 1.8 :is di ected to a p ot -tub 2:0) m htzfromt erlamp 18' passes (to a irro .2

and is r flected therefrom. as indicated by th 3 s dash lines 82, 84-, respectively, to the photo-tube. If desired, the light source may be on one side of the conveyor and the photo-tube on the other, so that the objects ma, Nib, etc.-, moving along the conveyor i2 cut the beam of light passing to the photo-tube. A special method of adjustment of the transmitted and reflected beams 'is described hereinaftefi.

Referring now to Figure 2, the photo-tube 20 (which may be an RCA type 868) has an anode 24 and a cathode 26, connected by conductor 30 and by resistor 54 and conductor 64, respectively to; the respective ends 68 and of a secondary winding 32 of a transformer 28. The" primary winding 34 of this transformer is connected to'as'ource of alternating current (not shown) which may have an M S. vvalue rexampla: 22.0 vo ts-2.2.:

An auxiliary secondary winding 36 of the same of the lamp l8; alternatively, the secondary winding 32 maybe-tapped for this purpose.

' The photo-tube isconnected to ages tube40, having an anode 42, acathode 44 and a control glldf45. In a preferred embodiment, a tetrode RCA type 2051; having a screen 'grid48 connected to the cathode 44 by a conductor .56, has been used. The cathode 2'6 of'the photo-tube 20 is connected to the control grid 46 of the gas tube by a conductor 66 and resistor .52; the latter'ma havea value of 5.6 megohms; V i

V The Tanode 42 of the gas tube is connected through an energizingcoil 66 of a relay 62 to the .end68 of the'secondary winding '32; a conductor -l2.extends from a tap 1.4 on the secondary w o the cathode 44 ofthe gas tube. A capac- :itor 56 is connected .acrossthe resistor 54 in the when itscontrol grid 15.111056 negative, and .vice

-versa. The parallel combination of resistor54 and condenser .56 constitutes. a timedelay vcir -c,uit,"tending to oppose any change in the poatential of the, grid, aswill appear more fully hereinafter; The wholev of: the secondary winding provides an alternating potentialbetween the anode and cathode of theyphoto-tube, but the voltage drop through the resistor .54 serves to -limit thevalue ofthis potential;

' Therelay 62 containsthe energizing coil 60 and an armature 76, which cooperateswith a switch-18 ina circuit 80 connected to the electric motora.

The operation of the circuit is asfollows: The bias on thecontrol grid 4'6 is of such a value as toprevent the gas tube from firing. Light from thelamp' l8 passes to the cathode 26 of the photo-tube 26; current flows therefromto the control grid 46 and raises its potential sufficiently to fire the gas tube. Current then flows in the anode circuit of the gas tube, energizes the coil 60 and therefore closes theswitch 78 and the circuit 36. As each object moves along the confve'yor l2, it interrupts the beam of light passing to-the photo-tube; and this, butfor the time eeny circuit, would extinguish current in the gas nels.

' 4 tube, open the relay 62 and, therefore, prevent the continued movement of the objects; The time delay circuit, however, is able to maintain the grid 46 above itseXtinguishing potential for a period dependent on its time constant. If the time which; it takes an object to cross the light beam passing to the photo-tube is less than the period cdrresponding to the jtimepj'onstantof the delay circuitylight again ;-passes to the cathode of the photo-tube and causes the grid 46 to remain at sufliciently positive potential to main v the relay-and preventing further movement of transformer provides voltage to heat thefilamen-t the objects along the conveyor. Removal of the impediment to thepassage of light to the phototube automatically 1 makes: the control operative again closesqthel relay.and sets the, objects in motion alongthe conveyor. Other circuits which have been proposed for thispurposerequire re-" setting by hand. .,,,'Ine.period, therefore, during which light pass ing to thelphoto-tube may be interrupted without extinguishing the current in the gas tube, is dependent .on the values of theelements in the time. delay circuit. In a preferred embodiment of the invention, the resistor 54and capacitor 56 had values of 1.2 megohms and ..5 microfarad, respectively, for an effective'tirne delay of approximateiy .5 second; the time, may be doubled or quadrupled by increasing the value of the capaccapacitor 56 will then be selected to ,provide'for the delay desired. In'the three examples just given, the value of the resistor was 1.2 megohms 'in eachcaseyit isgnot. desirable to increase the value :of .the resistor :above 5 megohms, because in electronic circuits the charge on the'condenser may then tend The resistor 52 matches the low impedance of thegas tube when conducting, with the comparatively high impedance of the resistor-capacitor combination 54-56; which would otherwise -be in'efiective for delaying the extinguishment of .the anode current ofthe tube. 4 r

It has beenproposed to provide a photo-electric relay operated by alternating current with means for 'maintaininga positive voltage on the grid of an-electron discharge amplifier durlng part of the negative half-cycle of the supply voltage. The present invention diners from that proposal in that thegrid'is held positive over a large number of complete cycles. v Certain variations in the embodiment described will suggest themselves to those skilled in the art. For example, the objects moving along the conveyor have been described as interrupting completely the passage of light to the cathode. of etheqphoto-tube, buta similar control effect may to .leak off through other chanarrests warning light, or otherwise to'indicate that the passage of objects along the conveyor is abnorma]. The current may also be used to actuate a combination of the movement-terminating and indicating means. I

When the objects passing along the conveyor are of irregular outline, the use of a beam passing to a. mirror and reflected therefrom to the photo-tube, as before described, has special advantages. For example, in Figure 3 the object is shown as a bottle Illa of the type which is ordinarily used for carbonated beverages, and which has a neck 86, a wide portion 88, and below that a narrower waist-like portion 90. The transmitted beam 82 may then be made substantially horizontal, and adjusted to such a height that if the bottles are jammed against each other in a horizontal position, the neck 86 of a bottle will be bound to interrupt the passage of light to the mirror, and thence to the tube. The beam may also be reflected upwards (for example, by inclining the mirror 22 at an angle to the vertical) so that it passes through the wide portion 88 of the bottle; if the bottles become jammed in a vertical position, the reflected beam 84 will be bound to be interrupted.

There has thus been described a control system for the movement of objects along a path in spaced relation, including a photo-tube and a gas tube operated by alternating current, and in which a, time delay circuit is employed to prevent the operation of the control on a variation in the energizing light for a predetermined period.

I claim as my invention:

1. A control system for apparatus adapted to move light-impeding objects along a path in spaced relation, including in combination a lightsensitive device, terminal means for applying alternating currents to said device, a source of light passing to said device across said path, and means responsive to the flow of current through said device and including a time delay circuit and a gas tube for terminating the movement of said objects on a variation of said light passing to said device for a period dependent on the time constant of said circuit.

2. In combination, means for moving light-impeding objects along a path in spaced relation, 2. light-sensitive device, terminal means for applying alternating currents to said device, a source of light passing to said device across said path, and means responsive to the flow of current through said device and including a time delay circuit for rendering said moving means inoperative on a variation of said light passing to said device for a period dependent on the time constant of said circuit.

3. In combination, a circuit including a normally closed relay and means for moving lightimpeding objects along a path in spaced relation, a control system for said circuit including a lightsensitive device, terminal means for applying alternating currents to said device, a source of light passing to said device across said path, and

' 6 a-co'nnection between said device and said relay, said connection including a time delay circuit and means responsive to the flow of current through said device for opening said relay on a variation ofsaid light passing to said-device for a-period dependent on the time constant of said time delay circuit. a 4, In combination, a circuit for moving lightimpeding objects along'a path in spaced relation, a light-sensitive device having at least an anode and a cathode, a source of light passing tosaid cathode. across said path, a. gas tube having at least an anode, a. cathode and a. grid and anormally closed relay with its energizing winding connecting the anode and cathode of said gas tube, a connection including a time delay circuit and a resistor in series between the cathode of said device and said grid and, a connection for applying alternating currents to said device and said tube, said relay being operatively connected with said first-mentioned circuit, whereby said first-mentioned circuit is rendered inoperative on a variation of said light passing to the cathode of said device for a period dependent on the time constant of said time delay circuit.

5. A control system for apparatus adapted to move light-impeding objects along a path in spaced relation, including in combination a lightsensitive device, terminal means for applying alternating currents to said device, a source of light passing to said device across said path, and means responive to the flow of current through said device and including a time delay circuit, for indicating a variation of said light passing to said device for a period dependent on the time constant of said circuit.

6. A control system for apparatus adapted to move light-impeding objects along a path in spaced relation, including in combination a lightsensitive device, terminal means for applying alternating currents to said device, a source of light passing to said device across said path, an instrument having at least two conditions, means for maintaining said instrument in one of said conditions, and means responsive to the flow of current through said device and including a time delay circuit, for conditioning said instrument to another of said conditions on a variation of said light passing to said device for a period dependent on' the time constant of said time delay circuit.

7. A control system for apparatus adapted to move light-impeding objects along a path in spaced relation, including in combination a lightsensitive device, terminal means for applying alternating currents to said device, a source of light, means defining a transmitted and a reflected path for said light from said source to said device, the path of said objects intersecting both said transmitted and said reflected paths, an instrument having two different indicating conditions, means initiated by the passage of light to said device for maintaining said instrument in one of said indicating conditions, and means responsive to the flow of current through said device and including a time delay circuit, for conditioning said instrument to another of said indicating conditions on a variation of said light passing to said device for a period dependent on the time constant of said time delay circuit.

8. In combination, a light-sensitive device having at least an anode and a cathode, a source of light passing to said cathode, a gas tube having at least an anode, a cathode and a grid, a connection for applying alternating currents to said device and said tube to maintain the; anode of said device and the'anfode and cathode of said tube at at least their respective operating potentials and to maintain saidggrid at below its firin potential, an electro-responsive; instrument connected to the anode ofsaid tube and having at least two indicating conditions,- a connection between the cathode of said device and said grid whereby said light passing to said cathode causes current to flow to said grid to fire said tube, and thereby to maintain said instrument in one of saidindicatingconditions; and a time delay circuit anda resistor in series therewith in the cir-- cuit of said grid for maintaining said 'grid at 8 dependent on the time constant of said time delay circuit, notwithstanding interruption of Y said light passing to said cathode. v V t JAMES H. REYNOLDSQ;

, REFERENCES CITED 7 The following references are of record in the file of this patent: 1 1

UNITED STATES PATENTS Number 7 Name I 7 Date 2,150,467 Stain Mar. 14,1939 1,998,132 Geficken Apr'. 16, 1935 1,972,682 Fitzgerald Sept. 4, 1934 Cockrell Feb. 19, 1935 

